In Positron Emission Tomography (abbreviated as PET herein), the distribution of a tracer marked with positron nuclides is acquired by capturing gamma photons emitted due to annihilation of the positron in the human body, thereby pathophysiological features such as the function of an organ and metabolism are acquired. The imaging performance of the system is directly affected by the accuracy in acquiring energy, detected position and time information of gamma photons. A scintillation pulse sampling and processing unit is a crucial core component in a PET system with a main function to process the scintillation pulse sampled by a front-end detector and to obtain the energy, location and time information of gamma photons. It is desirable that the scintillation pulse sampling and processing unit has high accuracy, stable performance, convenience in real-time correction, high integrity and other character, to ensure the performance of the PET system.
The scintillation pulse sampling and processing unit in the conventional technology is generally a hybrid system mixed by an analog circuit and a digital circuit. The scintillation pulse information is mostly extracted by the analog circuit, and the digital circuit is mainly used to collect, store and transfer the corresponding information. The PET system using such scintillation pulse sampling and processing unit is difficult to implement real-time correction and thereby has critical demand for working environment.
The above problem can be solved by designing an all-digital PET system. To implement an all-digital PET system, total digitalization of the scintillation pulse sampling and processing unit may firstly be implemented. In designing and implementing of the totally digitalized scintillation pulse sampling and processing unit, a method and device for digitalizing scintillation pulses based on prior knowledge is proposed by Qingguo Xie et. al. (Xie, Q. and Kao, C. M. and Wang, X. and Guo, N. and Zhu, C. and Frisch, H. and Moses, W. W. and Chen, C. T., “Potentials of digitally sampling scintillation pulses in timing determination in PET”, IEEE Transactions on Nuclear Science, vol. 56 pp. 2607-2613 2009). In this method, the time when a pulse exceeds a predefined threshold is acquired by using a threshold comparator and a time-digitalizing device to implement a sparse sampling on the scintillation pulse time axis. The scintillation pulse is rebuilt according to the acquired sampling data and a scintillation pulse module, and the information of the scintillation pulse is extracted based on the rebuilt scintillation pulse. The method provides a low cost solution for digitalizing the scintillation pulse. By increasing the number of thresholds, more sampling data may be acquired and the accuracy of rebuilding the pulse and extracting the corresponding information may be improved. However, it also means that more threshold comparators have to be employed in the system, resulting in significantly increasing system power consumption, lower system integration level and higher system cost.
Therefore, specific to the problems in current pulse sampling and processing technology, it is necessary to provide a new digitalized method and device for sampling and processing scintillation pulse, to overcome the disadvantages of the scintillation pulse sampling and processing unit in the conventional technology.